Push button keys

ABSTRACT

THE IMPROVED CONSTRUCTION OF PUSH BUTTON SWITCH UNIT INCORPORATING MICRO-SWITCH UNITS.

E. FRYDMAN PUSH BUTTON KEYS March 2, 1971 2 Sheets-Sheet 8 Filed Jan. 15, 1969 INVENT R ATTORNEY$ Emah L cZ 698 United States Patent U.S. Cl. 74-107 2 Claims ABSTRACT OF THE DISCLOSURE The improved construction of push button switch unit incorporating micro-switch units.

This invention relates to push button switch units and more particularly to such units which incorporate microswitches arranged to be operated by a push button key.

Push button keys are available in several versions to meet the varying requirements. These broadly comprise a simple push key which only remains operated so long as manual pressure is applied, a push-to-operate-push-torelease key (push-push), a push to operate key which is released by operating a further key (mutual interlock) and a push key forming one of a group of keys in which only one key can be operated at a time (mutually exclusive). Each or any of these types are required in illuminated (lamp in the housing which causes the key knob to be illuminated) and non-illuminated versions.

Generally speaking, each key type is manufactured to perform only a few of these required functions and one object of the present invention is to provide a multi-purpose key for operating microswitches incorporated in a switch unit.

According to the invention there is provided a push button switch unit comprising a housing, a push button mounted so as to project at one end thereof into said housing and movable to increase the extent of projection of said one end into said housing against a spring restoring force, a switch actuating plate pivotally mounted at one end within said housing, spring means disposed within said housing to act between said one end of said push button and said actuating plate, and at least one microswitch arranged to be actuated by pivoting movement of said actuating plate in response to movement of said push button into said housing.

The various features and advantages of the present invention will be apparent from the following description of embodiments thereof taken in conjunction with the accompanying drawings,

FIG. 1 is a side elevation of a push-push key with part of the support frame and the track pin removed.

FIG. 2 is a first angle projection of FIG. 1 and FIG. 2(a) shows a detail of FIG. 2,

FIG. 3 is a plan version of the lever plate,

FIG. 4 shows the track used for a push-push action,

FIG. 5 shows a method of providing mutually exclusive operation,

FIG. 6 shows the track used for mutual interlock action,

FIG. 7 shows an alternative form of operating spring, and

FIG. 8 shows a means for operating additional microswitches.

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Referring now to FIG. 1, the push key comprises a moulded cap or button 1 fitted onto a hollow shank 2 forming part of a moulding which also comprises stop plate 3, track member 4, and spring retaining pins 5 and 6.

A further retaining pin 7 is fixed to a U-shaped lever plate 8 (see FIG. 3) which is pivoted at points 9 and 10 (FIG. 2).

The lever plate 8 bears lightly on the operating button 11 of a microswitch 12.

An operating spring 13 is retained between spring retaining pins 5 and 7 and a restoring spring 14 is located at one end on spring retaining pin 6 and, at the other end, is located on spring retaining pin 15 mounted on an intermediate block 16 (FIG. 2).

Referring now to FIG. 2, a track pin assembly 17 is pivoted on a centre 18 and the pin 19 rests in the U- shaped track 21. The operation of the pin and track to provide a push-push operation is fully described in British Patent No. 958,663.

The hollow shank 2 passes through an externally threaded push 22 fixed to the U-shaped support frame 20 and the stop plate 3 is pressed against the top inner face of support frame 20 by the action of restoring spring 14. Thi represents the normal position of the key.

Two flat leads 23, 24 support and provide electrical connections to a lamp holder (not shown) in the hollow shank 2. These two fiat leads are held in place by slots in the intermediate block 16 and are extended to provide electrical terminal connections 25, 26.

The intermediate block -16 also acts as a spacer between two microswitches 12 and 27 and these three members are located and secured by mean of rivet passing through both sides of the support frame 20 and the holes 28, 29 in the microswitches 12 and 27 and also in the intermediate block 16. The three electrical terminals of each of the microswitches are shown at 31a, 31b, 32a, 32b, 33a, and 33b.

For convenience and clarity, the operating and restoring springs 13 and 14 respectively are omitted from FIG. 2.

Still referring to FIG. 2, the stop plate 3 has a cylindrical extension 34 which moves vertically in slot 35 as shown in FIG. 2(a).

The operation of the unit as a push-push key will now be described, mainly with reference to FIG. 4, which shows the track member 4 forming an extension of stop plate 3 and having a V-shaped track 21. Four positions of the pin 19 are shown as 19a, 19b, 19c, and 19d. It is to be assumed that the pin 19 is urged towards the left in FIG. 4 by bias spring 36 (FIG. 2). With the push key in the normal (unoperated) condition, pin .19 occupies position 19a in track 21. As the button 1 is pressed downwards, the pin 19 rides up the right hand portion of track 21. This is ensured by the provision of the nonreturn step 37 which prevents pin 19 from entering the left hand portion of track 21. When the button 1 is fully depressed, the microswitches are operated and pin 19 occupies position 1%. On release of the button, pin 19 settles back in position 190, in which position the microswitches remain operated, as will be explained later. On the next operation of button 1, pin 19 occupies position 19d and, on release of the button, the pin rides down the left hand side of the track, drops down the non-return step 37 and reverts to position 19a.

From the above described operation, it can be seen that the button assembly partially restores on the first release motion. The microswitches .12 and 27, therefore, have to operate when the button is fully depressed (pin 19 in position 191?) and remain operated when the button partially restores (pin 19 in position 190).

In the push button key according to the invention, use is made of the fact that a microswitch will remain operated with considerably less force exerted on the operating button 11 than that required to operate it. On initial operation, with the button fully depressed, stop plate 3 exerts sutficient force via operating spring 13 on the lever plate 8 to cause the microswitch to operate. On initial release of the button, the stop plate 4 partially restores to the position represented by pin position 190. Although the force exerted by operating spring 13 is reduced it is still sufficient to maintain the microswitch in the operated condition. This situation is readily achieved since, in general, the force required to maintain the microswitch operated is of the order of one third of the force required to operate it.

On the next operation and release of the button 1, the pin 19 restores to position 19a and the key is now at the normal position. The retraction of stop plate 3 has withdrawn operating spring 13 and the microswitch contact is released. Spring 14 supplies the restoring force to the stop plate 3 and, hence, the associated assembly of shank 2 and cap 1.

In order to prevent strain on pin 19 during the released condition, the track 21 is so arranged that, with the support frame 20 acting as a back-stop for stop plate 3, the pin 19 does not touch the lower extension of track 21, as shown at position 190 in FIG. 4.

Also, when the button is fully operated, the underside edge 38 of moulded cap 1 abuts the upper edge of bush 22. In this condition, pin 19 is just clear of the upper edge of track 21 as shown in positions 1% and 19d of FIG. 4 and cannot, therefore, be damaged by punch operation of the key.

During the various operating actions, the cylindrical extension 34, attached to stop plate 3, is moving up and down the slot 35. This pin has two functions. Firstly, it helps prevent any slight rotation of stop plate 3 and, hence, cap 1. This enables a strip of adjacently-mounted keys to line up reasonably accurately with each other.

The second function is to provide mutually exclusive action between a gang of keys. The extension piece 34 acts as an interference piece between a series of balls, discs, plates, or the like, which have a total freedom of sideways movement greater than the diameter of extension 34 and less than twice its diameter. An example of such an action is shown in FIG. 5, !Where thin plates 41 to 45 are constrained to move freely in a sideways direction only. The extensions 34- of four adjacent push keys are represented by 34a, 34b, 34c, and 34d. The push button represented by extension 34c is operated and plates 42, 43, 44, have been pushed sideways to make sufiicient clearance. It can be seen that the position of the plates now prevents the operation of any other keys. Plates 41 and 45 never need to move, of course, and remain adjacent the end stops 46 and 47 respectively.

It can also be appreciated that, if two keys are operated simultaneously, the plates would readjust such that both keys could only be operated a small amount-insutfiicient, in fact, to operate the microswitch.

Referring again to FIG. 2, a further track member 4a is provided on the opposite side of the stop plate 3. This track member is shown in FIG. 6. The pin operation is the same as that already described, i.e. biased to the left of the figure. In the normal condition, pin 19 is at position 19a. When the key is operated, the pin slides up the ramp and then springs into position 1%. The key is now in a locked position and cannot be released by further operation of the same key. In this case, a series of keys have their pin assemblies 17 (FIG. 2) connected together. The

operation of another key causes all pins 19 to move to the right, whereupon the locked key is released by the other key (when the pin of the latter rides up the ramp) and moves pin 19 of the locked key from its position 1% until it clears the step of the ramp. The locked key is then fully released by the restoring spring 14. This pro vides the well known mutual interlock facility.

The tension gradient of spring 13 can be chosen to operate the microswitches when pin 19 enters the latching position 19c, This arrangement ensures that, if the push key is not operated fully, the microswitches will not operate and key will not lock.

It can thus be seen that either a push-push or a mutual interlock action can be provided according to which track (FIG. 4 or FIG. 6) is assembled adjacent to the pin assembly side of the key.

When the key is required as a simple push key (no locking action) the pin assembly 17 is not fitted.

In this manner, the one key can be assembled in order to provide push-push, mutually exclusive mutual interlock, or simple push actions as required.

Referring now to FIG. 7, the operating spring 13 has been replaced by a leaf or blade spring 51. The rest of the drawing is exactly the same as for FIG. 1. This provides a simple means of adjustment of the operating spring by the well-known method of stroking.

If the push key is required to operate more than the two microswitches shown hitherto without increasing the area occupied on the fascia or panel on which the keys are mounted, the additional microswitch may be conveniently mounted as shown in FIG. 8.

In this figure, the upper portion of the key is exactly as shown in FIGS. 1 and 2. An operating rod 52, having a flange 53, rests lightly against the underside of lever plate 8. An identical lever plate 55 operates the additional microswitch(es) 56- (57) in the same fashion as described for microswitches 12 and 27. A further operating spring '54 is located between the flange 54 and the spring retaining pip 58. The spring 54 now acts in the identical manner to operate the additional microswitch(es) as described in respect to spring 13. Also, in similar fashion, spring 54 may be replaced by a blade spring as shown in FIG. 7.

It can also be seen that the lamp leads have been extended beyond the additional microswitches in order to be accessible for termination from the bottom of the key in the same manner as shown in FIGS. 1 and 2.

A further advantage of the present invention can now be appreciated, namely that the microswitch is not operated directly from the push button, but is buffered by the spring 13. This helps reduce possible damage to the microswitch by repeated punching of the key. Further, the presence of this spring enables a comparatively large movement of the button (required to operate the tracking sequence) to be translated into the small movement required to operate the microswitch.

I claim:

1. In a push button switch unit comprising a housing, a push button mounted so as to project at one end thereof into said housing and movable to increase the extent of projection of said one end into said housing against a spring restoring force, the provision of a switch actuating plate pivotally mounted at one end within said housing, spring means disposed within said housing to act between said one end of said push button and said actuating plate, said spring means being a compression spring disposed to engage said plate at one end and, at its opposite end, to engage said push buton, and at least one microswitch arranged to be actuated by pivoting movement of said actuating plate in response to movement of said push button into said housing.

2. In a push button switch unit comprising a housing, a push button mounted so as to project at one end thereof into said housing and movable to increase the extent of projection of said one end into said housing against a spring restoring force, the provision of a switch actuating plate pivotally mounted at one end Within said housing, spring means disposed within said housing to act between said one end of said push button and said actuating plate, said spring means being a blade spring anchored at one end to said actuating plate and projecting away from such plate towards an inwardly projecting extension of said push button, and at least one microswitch arranged to be actuated by pivoting movement of said actuating plate in response to movement of said push button into said housing.

References Cited UNITED STATES PATENTS Cousins 200--153.9 Bury 200160 Wright 200160 Gaber 200153.9 

